1. Field of the Invention
The present invention relates to a pre-oriented, non-stretched polyester fiber (POY fiber), spun at spooling speeds of at least 3,000 m/min., which is well-suited for processing by means of stretch texturing at speeds of over 500 m/min., as well as a process for the production of the same.
2. Summary of the Related Art
The development of a process for the production of POY polyester fibers, which can be stretch-textured at speeds of over 500 m/min., is of great economic interest, since at these speeds the investment expended per kg of POY fibers is reduced. Furthermore, the speed of fiber production can be significantly increased. A non-modified polyethylene terephthalate with a breaking elongation of approximately 110 to 125% corresponding to a spooling speed of approximately 3200 to 3400 m/min. is necessary for the stretch texturing at approximately 500 m/min. If the spooling speed is increased, the increased orientation of the fibers reduces elongation, which, in turn, compels a reduction of the stretch texturing speed. Ultimately, texturing becomes impossible since the fiber capillaries break under the torsion stressing.
An increase in the stretch texturing speed may be accomplished by the addition of up to 10 meq/kg of certain chain-branching substances, such as pentaerythrite, trimethylolpropane, mellitic acid or timer acid (GB patent number 1 553 020), trimesinic acid or trimellitic acid (European patent number EP 0 263 603), or tetraethyl silicate (U.S. Pat. No. 4,966,740), during the production of polyester. The use of the polyhydroxy compounds limits the texturing speed to less than 200 m/min. The addition of polycarboxylic acids or tetraethyl silicate produces fiber of varying quality due to the formation of volatile ethylene glycol esters or decomposition through reaction water, respectively. All of these chain-branching additives are to some degree toxic. Decreased texturing speed and increased fluctuations in fiber quality and toxicity are some of the disadvantages of the chain branching substances of the prior art.
In the production of polyester, it is generally known to add carboxy phosphonic acid compounds of the formula: ##STR2## after the reesterification process but prior to polycondensation for the complexing to and inactivation of the reesterification catalyst. U.S. Pat. No. 4,254,018, European patent, EP 0 699 700 A, and Japanese patent JP 49-125 494 A describe compounds where R.sup.1, R.sup.2, R.sup.3 are alkyl groups and U.S. Pat. No. 3,169,944 describes compounds where R.sup.1, R.sup.2, R.sup.3 are --H or alkyl groups. In no example are R.sup.1, R.sup.2, R.sup.3 all hydrogen. None of these references describes the production of POY fibers or stretch texturing.
U.S. Pat. No. 4,086,208 describes the addition, at the beginning of the esterification or reesterification, of 500 to 50,000 ppm of phosphorus of the compound above, wherein R.sup.1, R.sup.2 and R.sup.3 are hydrocarbon radical or --H. Subsequent polycondensation followed by conventional methods of spinning and stretching produces polyester fibers with improved flame resistance. Examples with compounds in which R.sup.1, R.sup.2 and R.sup.3 are hydrogen are absent in these references. Also, neither stretch texturing speeds of over 500 m/min. nor the production of POY fibers suited to stretch texturing is disclosed.